From: Reinette Chatre <reinette.chatre@xxxxxxxxx>
Calling cancel_delayed_work() from inside
spin_lock_irqsave, introduces a potential deadlock.
As explained by Johannes Berg <johannes@xxxxxxxxxxxxxxxx>
A - lock
T - timer
phase CPU 1 CPU 2
---------------------------------------------
some place that calls
cancel_timer_sync()
(which is the | code)
lock-irq(A)
| "lock-irq"(T)
| "unlock"(T)
| wait(T)
unlock(A)
timer softirq
"lock"(T)
run(T)
"unlock"(T)
irq handler
lock(A)
unlock(A)
Now all that again, interleaved, leading to deadlock:
lock-irq(A)
"lock"(T)
run(T)
IRQ during or maybe
before run(T) --> lock(A)
"lock-irq"(T)
wait(T)
We fix this by moving the call to cancel_delayed_work() into workqueue.
There are cases where the work may not actually be queued or running
at the time we are trying to cancel it, but cancel_delayed_work() is
able to deal with this.
Also cleanup iwl_set_mode related to this call. This function
(iwl_set_mode) is only called when bringing interface up and there will
thus not be any scanning done. No need to try to cancel scanning.
Fixes http://bugzilla.kernel.org/show_bug.cgi?id=13224, which was also
reported at http://marc.info/?l=linux-wireless&m=124081921903223&w=2 .
Tested-by: Miles Lane <miles.lane@xxxxxxxxx>
Signed-off-by: Reinette Chatre <reinette.chatre@xxxxxxxxx>
Acked-by: Zhu Yi <yi.zhu@xxxxxxxxx>
---
drivers/net/wireless/iwlwifi/iwl-core.c | 7 -------
drivers/net/wireless/iwlwifi/iwl-scan.c | 7 ++++---
drivers/net/wireless/iwlwifi/iwl3945-base.c | 2 ++
3 files changed, 6 insertions(+), 10 deletions(-)
diff --git a/drivers/net/wireless/iwlwifi/iwl-core.c b/drivers/net/wireless/iwlwifi/iwl-core.c
index 5393fb3..967343a 100644
--- a/drivers/net/wireless/iwlwifi/iwl-core.c
+++ b/drivers/net/wireless/iwlwifi/iwl-core.c
@@ -2437,13 +2437,6 @@ int iwl_set_mode(struct iwl_priv *priv, int mode)
if (!iwl_is_ready_rf(priv))
return -EAGAIN;
- cancel_delayed_work(&priv->scan_check);
- if (iwl_scan_cancel_timeout(priv, 100)) {
- IWL_WARN(priv, "Aborted scan still in progress after 100ms\n");
- IWL_DEBUG_MAC80211(priv, "leaving - scan abort failed.\n");
- return -EAGAIN;
- }
-
iwlcore_commit_rxon(priv);
return 0;
diff --git a/drivers/net/wireless/iwlwifi/iwl-scan.c b/drivers/net/wireless/iwlwifi/iwl-scan.c
index 8029206..41358cf 100644
--- a/drivers/net/wireless/iwlwifi/iwl-scan.c
+++ b/drivers/net/wireless/iwlwifi/iwl-scan.c
@@ -227,9 +227,6 @@ static void iwl_rx_scan_complete_notif(struct iwl_priv *priv,
/* The HW is no longer scanning */
clear_bit(STATUS_SCAN_HW, &priv->status);
- /* The scan completion notification came in, so kill that timer... */
- cancel_delayed_work(&priv->scan_check);
-
IWL_DEBUG_INFO(priv, "Scan pass on %sGHz took %dms\n",
(priv->scan_bands & BIT(IEEE80211_BAND_2GHZ)) ?
"2.4" : "5.2",
@@ -591,6 +588,8 @@ static void iwl_bg_request_scan(struct work_struct *data)
mutex_lock(&priv->mutex);
+ cancel_delayed_work(&priv->scan_check);
+
if (!iwl_is_ready(priv)) {
IWL_WARN(priv, "request scan called when driver not ready.\n");
goto done;
@@ -816,6 +815,8 @@ void iwl_bg_scan_completed(struct work_struct *work)
IWL_DEBUG_SCAN(priv, "SCAN complete scan\n");
+ cancel_delayed_work(&priv->scan_check);
+
priv->scan_request = NULL;
ieee80211_scan_completed(priv->hw, false);
diff --git a/drivers/net/wireless/iwlwifi/iwl3945-base.c b/drivers/net/wireless/iwlwifi/iwl3945-base.c
index 5d52f22..ded7fea 100644
--- a/drivers/net/wireless/iwlwifi/iwl3945-base.c
+++ b/drivers/net/wireless/iwlwifi/iwl3945-base.c
@@ -2995,6 +2995,8 @@ static void iwl3945_bg_request_scan(struct work_struct *data)
mutex_lock(&priv->mutex);
+ cancel_delayed_work(&priv->scan_check);
+
if (!iwl_is_ready(priv)) {
IWL_WARN(priv, "request scan called when driver not ready.\n");
goto done;
--
1.5.6.3
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